1. Field of the Invention
The invention relates generally to self-deploying, helical structures and more particularly to a self-deploying helical structure employed as an antenna.
2. Description of the Related Art
Helical antennae are generally well-known in the art. While some helical antennae are designed to be permanent and stationary in their operating configuration, it is often desirable to have an antenna capable of being transported and then deployed into its extended operating configuration. Thus, many attempts have been made to design helical antennae capable of being collapsed and transported and then deployed into the extended operating configuration.
For example, U.S. Pat. No. 3,836,979 to Kurland et al. for a "Lightweight Deployable Helical Antenna" discloses a helical antenna coiled about a longitudinally extendable and contractible supporting structure comprising a truss frame constructed of resiliently flexible strain energy beams. The antenna is collapsible to a relatively compact configuration for stowage and erects automatically, when released, under the force of the strain energy stored in the antenna beams.
U.S. Pat. No. 4,068,238 to Acker for an "Elastic Strain Energy Deployable Helical Antenna" also discloses a helical antenna having a tubular resiliently flexible antenna element fixed at one end to a support and formed into a normally extended, resiliently compressible helix. The antenna includes a plurality of flexible tension members of shorter overall length than the axial length of the helix if the helix were allowed to become fully extended. The flexible tension members are fixed at one end to the support, extend axially of the helix, and are secured to its helical turns. The antenna is compressible axially for storage and is deployable axially by stored elastic strain energy to an extended operating length at which the tension members are stressed in tension by the helix to reinforce the latter against deflection laterally of its longitudinal axis.
U.S. Pat. No. 4,780,727 to Seal et al. for a "Collapsible Bifilar Helical Antenna," discloses a bifilar helical antenna wound about a rigid mast and a plurality of support arms. The support arms are slidable along the axis of the mast to allow for expansion and contraction of the helices. The mast includes multiple sections which can be added or removed to permit adjustment of the axial length of the mast.
U.S. Pat. No. 3,059,322 to Teague for a "Method of Making a Collapsible Antenna of Wire Mesh" discloses a collapsible antenna which can be rolled and unrolled manually into, respectively, a collapsed and extended condition. The antenna, which is not a helical antenna, is constructed of wire mesh.
While these antennae may be stored in a smaller volume in their collapsed state than in their deployed configuration, none provides the flexibility and compactness of the present invention. Moreover, unlike the antenna of the present invention, the helical antennae described in the foregoing patents, among other things, are only capable of longitudinal contraction. While such antennae may be acceptable for helical antennae being deployed on Earth, they are not adapted for automatic deployment from a compactly stowed to extended position on a spacecraft in space. Typically, a spacecraft deployable structure requires a mechanical means, such as a separate spring or motor, to supply the requisite motive force to extend the antenna from its collapsed state. Any mechanical failure results in such antenna not being properly deployed. Thus, a self-deploying antenna not susceptible to such mechanical failure is desirable.